The Potentiometric Analysis of Membrane Structure and Its Application to Living Animal Membranes

Abstract

In 1911 Loeb and Beutner concluded from experiments on the concentration potentials of the apple-skin that it is specifically permeable for cations. Since then electromotive forces produced by living membranes and organs in contact with salt solutions have often been used in analysing living membranes. In particular Osterhout has succeeded in elucidating the fine structure of the membrane of large plant cells by potentiometric analysis, while H~iber (1926) and others investigated the ion permeability of animal membranes. In spite of such important results, it is not yet quite clear, whether the cation or anion selectivity which can be deduced directly from the measured potential is due to the sieve structure of the membrane or its charge or its specific dissolving power, or to all these factors taken together. A more detailed analysis of these properties will therefore be possible only if it is based on quantitative relations between the measured potential and those properties of the membrane or of the living tissue which influence the passage of ions. In order to make a survey of all these factors it seems reasonable to visualize first of all the molecular structure of living membranes.Living membranes, or any other living matter, can be considered as a network of flexible primary valence chains, in particular protein chains (K. H. Meyer, 1928Meyer, , 1929 Seifriz, 1928). These chains are interlinked at definite places by secondary valences or cross-linkings, called by us "regions of contact" (ltaftstellen) and later by Frey-Wyssling (1938) "points of contact" (11aftpunkte).Intracellular fluid, ions, lipoids, and soluble globular proteins are located inside this network. The lipoids are mostly linked to apolar groups of the protein chains, for which the term lipophilic groupswas proposed, while the hydrophilic groups of the chains are surrounded by water or aqueous cellular liquid and the ionised groups, e.g. --COO-groups, are neutralised by mobile "counter-ions."A natural membrane can moreover consist of layers of different composition under which lipoid layers can exist, and these layers can in turn be formed of areas of different properties like a mosaic. Calculation of the Membrane PotentialIf a membrane, i.e. a layer of any kind separates two solutions of a binary electrolyte, an electromotive force E results from diffusion of the two solutions 353

Electrical Phenomena in Nerve

“…The failure of the anesthetics to produce a rise in potential such as occurs in frog nerve is probably due to the difference in membrane properties; muscle, which possesses membrane characteristics like those of the crab fibers, also shows no increase (unpublished). The same differences exist with respect to the action of CO2 on the polarization (36,46,48). This correlation between anion permeability and polarizability provides further evidence of the importance of the membrane in some of the phenomena which have been observed and may be of significance in the different effects frequently observed in the central nervous system of vertebrates.…”

Potentiometric estimation of charges in barnacle muscle fibers under internal perfusion

“…The observed type of behavior in the barnacle muscle fiber (see Tables 3 and 4) is in general accord with the TMS theory, according to which the membrane potential is made up of two Donnan potentials at the two membrane-solution interfaces and a diffusion potential existing across the membrane. The net membrane potential Em is given by (Meyer & Bernfeld, 1945, 1946 …”

“…A brief review of this method as applied to artificial membranes has been given by Lakshminarayanaiah (1965Lakshminarayanaiah ( , 1969a. Since the work of Meyer and Bernfeld (1946), this method has not been applied to any biological preparation because of the complexity of the biological systems and in particular to the inability to control the internal and external ionic environments of the cell membrane.…”

Oscillation of the electric potential of frog skin under the effect of Li+: Experimental approach

“…The present paper gives only our original experime, ntal data, i.e., data the necessity for which has emerged in the course of the theoretical elaboration and wlhich we have not found in the literature. The details of the theoretical treatment will be explained subsequently in two steps: (i) building of a local model of oscillations and (ii) explanation of how the local oscillators synchronize themselves in the form of an overall oscillation of the electric potential.Since Dubois-Raymond discovered in 1848 [5] the electromotive force of the frog skin, many studies have shown that the presence, in the external medium, of either Na + or Li +, was absolutely necessary to maintain the epithelium potential [7, 11,20]. K +, Cs +, Rb + or NH4 + are ineffective [33].…”

“…Since Dubois-Raymond discovered in 1848 [5] the electromotive force of the frog skin, many studies have shown that the presence, in the external medium, of either Na + or Li +, was absolutely necessary to maintain the epithelium potential [7,11,20]. K +, Cs +, Rb + or NH4 + are ineffective [33].…”